24.2.3.5 Semisynchronous Replication Plugins

MySQL replication is asynchronous by default. With
semisynchronous replication, a commit performed on the master
side blocks before returning to the session that performed the
transaction until at least one slave acknowledges that it has
received and logged the events for the transaction.
Semisynchronous replication is implemented through
complementary master and client plugins. See
Section 17.3.8, “Semisynchronous Replication”.